Temperature-controlled, phase-transition ultrasound imaging-guided photothermal-chemotherapy triggered by NIR light

Application of high intensity focused ultrasound combined with nanomaterials in anti-tumor therapy

High intensity focused ultrasound (HIFU) has demonstrated its safety, efficacy and noninvasiveness in the ablation of solid tumor. However, its further application is limited by its inherent deficiencies, such as postoperative recurrence caused by incomplete ablation and excessive intensity affecting surrounding healthy tissues. Recent research has indicated that the integration of nanomaterials with HIFU exhibits a promising synergistic effect in tumor ablation. The concurrent utilization of nanomaterials with HIFU can help overcome the limitations of HIFU by improving targeting and ablation efficiency, expanding operation area, increasing operation accuracy, enhancing stability and bio-safety during the process. It also provides a platform for multi-therapy and multi-mode imaging guidance. The present review comprehensively expounds upon the synergistic mechanism between nanomaterials and HIFU, summarizes the research progress of nanomaterials as cavitation nuclei and drug carriers in combination with HIFU for tumor ablation. Furthermore, this review highlights the potential for further exploration in the development of novel nanomaterials that enhance the synergistic effect with HIFU on tumor ablation.

Nanocarriers address intracellular barriers for efficient drug delivery, overcoming drug resistance, subcellular targeting and controlled release

The cellular barriers are major bottlenecks for bioactive compounds entering into cells to accomplish their biological functions, which limits their biomedical applications. Nanocarriers have demonstrated high potential and benefits for encapsulating bioactive compounds and efficiently delivering them into target cells by overcoming a cascade of intracellular barriers to achieve desirable therapeutic and diagnostic effects. In this review, we introduce the cellular barriers ahead of drug delivery and nanocarriers, as well as summarize recent advances and strategies of nanocarriers for increasing internalization with cells, promoting intracellular trafficking, overcoming drug resistance, targeting subcellular locations and controlled drug release. Lastly, the future perspectives of nanocarriers for intracellular drug delivery are discussed, which mainly focus on potential challenges and future directions. Our review presents an overview of intracellular drug delivery by nanocarriers, which may encourage the future development of nanocarriers for efficient and precision drug delivery into a wide range of cells and subcellular targets.

Biomedical Approach of Nanotechnology and Biological Risks: A Mini-Review

Nanotechnology has played a prominent role in biomedical engineering, offering innovative approaches to numerous treatments. Notable advances have been observed in the development of medical devices, contributing to the advancement of modern medicine. This article briefly discusses key applications of nanotechnology in tissue engineering, controlled drug release systems, biosensors and monitoring, and imaging and diagnosis. The particular emphasis on this theme will result in a better understanding, selection, and technical approach to nanomaterials for biomedical purposes, including biological risks, security, and biocompatibility criteria.

Hybrid Nanoplatforms Comprising Organic Nanocompartments Encapsulating Inorganic Nanoparticles for Enhanced Drug Delivery and Bioimaging Applications

Organic and inorganic nanoparticles (NPs) have attracted significant attention due to their unique physico-chemical properties, which have paved the way for their application in numerous fields including diagnostics and therapy. Recently, hybrid nanomaterials consisting of organic nanocompartments (e.g., liposomes, micelles, poly (lactic-co-glycolic acid) NPs, dendrimers, or chitosan NPs) encapsulating inorganic NPs (quantum dots, or NPs made of gold, silver, silica, or magnetic materials) have been researched for usage in vivo as drug-delivery or theranostic agents. These classes of hybrid multi-particulate systems can enable or facilitate the use of inorganic NPs in biomedical applications. Notably, integration of inorganic NPs within organic nanocompartments results in improved NP stability, enhanced bioavailability, and reduced systemic toxicity. Moreover, these hybrid nanomaterials allow synergistic interactions between organic and inorganic NPs, leading to further improvements in therapeutic efficacy. Furthermore, these platforms can also serve as multifunctional agents capable of advanced bioimaging and targeted delivery of therapeutic agents, with great potential for clinical applications. By considering these advancements in the field of nanomedicine, this review aims to provide an overview of recent developments in the use of hybrid nanoparticulate systems that consist of organic nanocompartments encapsulating inorganic NPs for applications in drug delivery, bioimaging, and theranostics.

The Application of Nanoparticle-Based Imaging and Phototherapy for Female Reproductive Organs Diseases

Various female reproductive disorders affect millions of women worldwide and bring many troubles to women's daily life. Let alone, gynecological cancer (such as ovarian cancer and cervical cancer) is a severe threat to most women's lives. Endometriosis, pelvic inflammatory disease, and other chronic diseases-induced pain have significantly harmed women's physical and mental health. Despite recent advances in the female reproductive field, the existing challenges are still enormous such as personalization of disease, difficulty in diagnosing early cancers, antibiotic resistance in infectious diseases, etc. To confront such challenges, nanoparticle-based imaging tools and phototherapies that offer minimally invasive detection and treatment of reproductive tract-associated pathologies are indispensable and innovative. Of late, several clinical trials have also been conducted using nanoparticles for the early detection of female reproductive tract infections and cancers, targeted drug delivery, and cellular therapeutics. However, these nanoparticle trials are still nascent due to the body's delicate and complex female reproductive system. The present review comprehensively focuses on emerging nanoparticle-based imaging and phototherapies applications, which hold enormous promise for improved early diagnosis and effective treatments of various female reproductive organ diseases.

Ultrasound contrast agents from microbubbles to biogenic gas vesicles

Microbubbles have been the earliest and most widely used ultrasound contrast agents by virtue of their unique features: such as non-toxicity, intravenous injectability, ability to cross the pulmonary capillary bed, and significant enhancement of echo signals for the duration of the examination, resulting in essential preclinical and clinical applications. The use of microbubbles functionalized with targeting ligands to bind to specific targets in the bloodstream has further enabled ultrasound molecular imaging. Nevertheless, it is very challenging to utilize targeted microbubbles for molecular imaging of extravascular targets due to their size. A series of acoustic nanomaterials have been developed for breaking free from this constraint. Especially, biogenic gas vesicles, gas-filled protein nanostructures from microorganisms, were engineered as the first biomolecular ultrasound contrast agents, opening the door for more direct visualization of cellular and molecular function by ultrasound imaging. The ordered protein shell structure and unique gas filling mechanism of biogenic gas vesicles endow them with excellent stability and attractive acoustic responses. What's more, their genetic encodability enables them to act as acoustic reporter genes. This article reviews the upgrading progresses of ultrasound contrast agents from microbubbles to biogenic gas vesicles, and the opportunities and challenges for the commercial and clinical translation of the nascent field of biomolecular ultrasound.

Evaluation of perfluoropropane (C3F8)-filled chitosan polyacrylic acid nanobubbles for ultrasound imaging of sentinel lymph nodes and tumors

Accurate sentinel lymph node (SLN) identification is an important prerequisite for sentinel lymph node biopsy (SLNB). However, existing SLN mapping techniques, mainly imaging-guided methods, are severely restricted by the high cost of the instruments, harmful radiation or unsatisfactory imaging depths. Herein, we prepared a new ultrasound contrast agent by filling perfluoropropane (C₃F₈) into chitosan polyacrylic acid nanobubbles for precise SLN identification. The obtained ultrasound contrast agent, coined C₃F₈-CS-PAA nanobubbles, presents a nanometer size with a diameter of approximately 120 nm. The C₃F₈-CS-PAA nanobubbles of desirable size are able to enter lymphatic vessels and accumulate in the sentinel lymph node to enhance ultrasound imaging. As a result, the injection of C₃F₈-CS-PAA nanobubbles can remarkably enhance the ultrasound imaging lymph system, providing image guidance for sentinel lymph node biopsy. Furthermore, it was shown that such C₃F₈-CS-PAA nanobubbles can effectively permeate into the tumor region via the tumor-enhanced permeability and retention (EPR) effect to enhance tumor ultrasound imaging for monitoring tumorigenesis. This work highlights a novel nanoscale ultrasound contrast agent for the lymphatic system and tumor imaging, with great promise for subsequent studies and clinical applications.

Ultrasound and nanomaterial: an efficient pair to fight cancer

Ultrasounds are often used in cancer treatment protocols, e.g. to collect tumor tissues in the right location using ultrasound-guided biopsy, to image the region of the tumor using more affordable and easier to use apparatus than MRI and CT, or to ablate tumor tissues using HIFU. The efficacy of these methods can be further improved by combining them with various nano-systems, thus enabling: (i) a better resolution of ultrasound imaging, allowing for example the visualization of angiogenic blood vessels, (ii) the specific tumor targeting of anti-tumor chemotherapeutic drugs or gases attached to or encapsulated in nano-systems and released in a controlled manner in the tumor under ultrasound application, (iii) tumor treatment at tumor site using more moderate heating temperatures than with HIFU. Furthermore, some nano-systems display adjustable sizes, i.e. nanobubbles can grow into micro-bubbles. Such dual size is advantageous since it enables gathering within the same unit the targeting properties of nano bubbles via EPR effect and the enhanced ultrasound contrasting properties of micro bubbles. Interestingly, the way in which nano-systems act against a tumor could in principle also be adjusted by accurately selecting the nano-system among a large choice and by tuning the values of the ultrasound parameters, which can lead, due to their mechanical nature, to specific effects such as cavitation that are usually not observed with purely electromagnetic waves and can potentially help destroying the tumor. This review highlights the clinical potential of these combined treatments that can improve the benefit/risk ratio of current cancer treatments.

Chemotherapeutic nanomaterials in tumor boundary delineation: Prospects for effective tumor treatment

Accurately delineating tumor boundaries is key to predicting survival rates of cancer patients and assessing response of tumor microenvironment to various therapeutic techniques such as chemotherapy and radiotherapy. This review discusses various strategies that have been deployed to accurately delineate tumor boundaries with particular emphasis on the potential of chemotherapeutic nanomaterials in tumor boundary delineation. It also compiles the types of tumors that have been successfully delineated by currently available strategies. Finally, the challenges that still abound in accurate tumor boundary delineation are presented alongside possible perspective strategies to either ameliorate or solve the problems. It is expected that the information communicated herein will form the first compendious baseline information on tumor boundary delineation with chemotherapeutic nanomaterials and provide useful insights into future possible paths to advancing current available tumor boundary delineation approaches to achieve efficacious tumor therapy.

Oxygen nanocarrier broke the hypoxia trap of solid tumors and rescued transfection efficiency for gene therapy

BACKGROUND

Gene therapy shows great promise for a broad array of diseases. However, we found that hypoxic tumor microenvironment (TME) exerted significant inhibitory effects on transfection efficiency of a variety of gene vectors (such as Lipo 2000 and PEI) in an oxygen-dependent manner. Solid tumors inevitably resulted in acute hypoxic areas due to the rapid proliferation of tumor cells and the aberrant structure of blood vessels. Thus, the hypoxic TME severely limited the efficiency and application of gene therapy.

METHODS

In our previous study, we constructed endoplasmic reticulum-targeted cationic liposomes, PAR-Lipo, which could effectively deliver genes and ensure high transfection efficiency under normoxia. Unsatisfactorily, the transfection efficiency of PAR-Lipo was rather poor under hypoxia. We believed that reoxygenation was the most direct and effective means to rescue the low transfection under hypoxia. Hence, we fabricated liposomes modified with perfluorooctyl bromide (PFOB@Lipo) to load oxygen and deliver it to tumor sites, which effectively alleviated the hypoxic nature of tumor. Then PAR-Lipo were applied to mediate high-efficiency delivery of tumor suppressor gene pTP53 to inhibit tumor progression.

RESULTS

The results showed that such staged strategy augmented the expression of P53 protein in tumors and extremely suppressed tumor growth.

CONCLUSION

This work was the first attempt to utilize an oxygen nanocarrier to assist the therapeutic effect of gene therapy under hypoxia, providing a new reference for gene therapy in malignant tumors. GRAPHICAL ABSTARCT.

Phototherapy and multimodal imaging of cancers based on perfluorocarbon nanomaterials

Phototherapy, such as photodynamic therapy (PDT) and photothermal therapy (PTT), possesses unique characteristics of non-invasiveness and minimal side effects in cancer treatment, compared with conventional therapies. However, the ubiquitous tumor hypoxia microenvironments could severely reduce the efficacy of oxygen-consuming phototherapies. Perfluorocarbon (PFC) nanomaterials have shown great practical value in carrying and transporting oxygen, which makes them promising agents to overcome tumor hypoxia and extend reactive oxygen species (ROS) lifetime to improve the efficacy of phototherapy. In this review, we summarize the latest advances in PFC-based PDT and PTT, and combined multimodal imaging technologies in various cancer types, aiming to facilitate their application-oriented clinical translation in the future.

Near infrared light fluorescence imaging-guided biomimetic nanoparticles of extracellular vesicles deliver indocyanine green and paclitaxel for hyperthermia combined with chemotherapy against glioma

Background

We investigated the therapeutic effect of targeting extracellular vesicles (EVs) loaded with indocyanine green (ICG) and paclitaxel (PTX) on glioma.

Methods

Raw264.7 cells were harvested to extract EVs for the preparation of ICG/PTX@RGE-EV by electroporation and click chemistry. We evaluated the success of modifying Neuropilin-1 targeting peptide (RGE) on the EV membrane of ICG/PTX@RGE-EV using super-resolution fluorescence microscopy and flow cytometry. Spectrophotometry and high performance liquid chromatography (HPLC) were implemented for qualitative and quantitative analysis of the ICG and PTX loaded in EVs. Photothermal properties of the vesicles were evaluated by exposing to 808-nm laser light. Western blot analysis, cell counting kit 8 (CCK-8), Calcein Acetoxymethyl Ester/propidium iodide (Calcein-AM/PI) staining, and flow cytometry were utilized for assessing effects of vesicle treatment on cellular behaviors. A nude mouse model bearing glioma was established to test the targeting ability and anti-tumor action of ICG/PTX@RGE-EV in vivo.

Results

Under exposure to 808-nm laser light, ICG/PTX@RGE-EV showed good photothermal properties and promotion of PTX release from EVs. ICG/PTX@RGE-EV effectively targeted U251 cells, with activation of the Caspase-3 pathway and elevated apoptosis in U251 cells through chemotherapy combined with hyperthermia. The anti-tumor function of ICG/PTX@RGE-EV was confirmed in the glioma mice via increased accumulation of PTX in the ICG/PTX@RGE-EV group and an increased median survival of 48 days in the ICG/PTX@RGE-EV group as compared to 25 days in the PBS group.

Conclusion

ICG/PTX@RGE-EV might actively target glioma to repress tumor growth by accelerating glioma cell apoptosis through combined chemotherapy-hyperthermia.

Graphic Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00907-3.

Multifunctional Magneto-Plasmonic Fe3O4/Au Nanocomposites: Approaching Magnetophoretically-Enhanced Photothermal Therapy

Magneto-plasmonic nanocomposites can possess properties inherent to both individual components (iron oxide and gold nanoparticles) and are reported to demonstrate high potential in targeted drug delivery and therapy. Herein, we report on Fe₃O₄/Au magneto-plasmonic nanocomposites (MPNC) synthesized with the use of amino acid tryptophan via chemical and photochemical reduction of Au ions in the presence of nanosized magnetite. The magnetic field (MF) induced aggregation was accompanied by an increase in the absorption in the near-infrared (NIR) spectral region, which was demonstrated to provide an enhanced photothermal (PT) effect under NIR laser irradiation (at 808 nm). A possibility for therapeutic application of the MPNC was illustrated using cancer cells in vitro. Cultured HeLa cells were treated by MPNC in the presence of MF and without it, following laser irradiation and imaging using confocal laser scanning microscopy. After scanning laser irradiation of the MPNC/MF treated cells, a formation and rise of photothermally-induced microbubbles on the cell surfaces was observed, leading to a damage of the cell membrane and cell destruction. We conclude that the synthesized magneto-plasmonic Fe₃O₄/Au nanosystems exhibit magnetic field-induced reversible aggregation accompanied by an increase in NIR absorption, allowing for an opportunity to magnetophoretically control and locally enhance a NIR light-induced thermal effect, which holds high promise for the application in photothermal therapy.

Light: A Magical Tool for Controlled Drug Delivery

Light is a particularly appealing tool for on-demand drug delivery due to its noninvasive nature, ease of application and exquisite temporal and spatial control. Great progress has been achieved in the development of novel light-driven drug delivery strategies with both breadth and depth. Light-controlled drug delivery platforms can be generally categorized into three groups: photochemical, photothermal, and photoisomerization-mediated therapies. Various advanced materials, such as metal nanoparticles, metal sulfides and oxides, metal-organic frameworks, carbon nanomaterials, upconversion nanoparticles, semiconductor nanoparticles, stimuli-responsive micelles, polymer- and liposome-based nanoparticles have been applied for light-stimulated drug delivery. In view of the increasing interest in on-demand targeted drug delivery, we review the development of light-responsive systems with a focus on recent advances, key limitations, and future directions.

Near-Infrared Responsive Phase-Shifted Nanoparticles for Magnetically Targeted MR/US Imaging and Photothermal Therapy of Cancer

Accurate diagnosis, providing guidance for early treatment, can greatly improve the survival rate of cancer patients. However, there are still some difficulties with the existing diagnostic technology and early treatment methods. Here, near-infrared responsive phase-shifted nanoparticles (NRPNs) have been designed for magnetically targeted MR/US imaging and photothermal therapy of tumors. In this study, we fabricated a multifunctional polymer nanoparticle encapsulating indocyanine green (ICG), magnetic Fe₃O₄ nanoparticles and perfluoropentane (PFP). Under laser irradiation, the NRPNs, which trigger a phase-shifted expansion effect due to the quick conversion from light to heat by ICG and Fe₃O₄, can be used for ultrasound (US) imaging. At the same time, such nanoparticles can kill cancer cells via photothermal therapy (PTT). As a kind of negative enhancement agent, magnetic Fe₃O₄ nanoparticles in NRPNs showed high spatial resolution in MR imaging. Moreover, with the help of the magnetic field, the NRPNs nanoparticles showed high cellular uptake and high tumor accumulation, indicating their magnetic targeting property without biosafety concerns. Therefore, we present a strategy for magnetically targeted MR/US imaging guided photothermal therapy for the accurate diagnosis and efficient treatment of tumors.

Application of Nanomaterials in Biomedical Imaging and Cancer Therapy

Nanomaterials, such as nanoparticles, nanorods, nanosphere, nanoshells, and nanostars, are very commonly used in biomedical imaging and cancer therapy. They make excellent drug carriers, imaging contrast agents, photothermal agents, photoacoustic agents, and radiation dose enhancers, among other applications. Recent advances in nanotechnology have led to the use of nanomaterials in many areas of functional imaging, cancer therapy, and synergistic combinational platforms. This review will systematically explore various applications of nanomaterials in biomedical imaging and cancer therapy. The medical imaging modalities include magnetic resonance imaging, computed tomography, positron emission tomography, single photon emission computerized tomography, optical imaging, ultrasound, and photoacoustic imaging. Various cancer therapeutic methods will also be included, including photothermal therapy, photodynamic therapy, chemotherapy, and immunotherapy. This review also covers theranostics, which use the same agent in diagnosis and therapy. This includes recent advances in multimodality imaging, image-guided therapy, and combination therapy. We found that the continuous advances of synthesis and design of novel nanomaterials will enhance the future development of medical imaging and cancer therapy. However, more resources should be available to examine side effects and cell toxicity when using nanomaterials in humans.

Perfluorocarbon nanodroplets stabilized with cisplatin-prodrug-constructed lipids enable efficient tumor oxygenation and chemo-radiotherapy of cancer

Concurrent chemo-radiotherapy has been widely applied for the treatment of a wide range of cancers, but its therapeutic efficacy against most solid tumors is severely impaired by their intrinsic hypoxic microenvironments. Utilizing the high oxygen loading capacity of perfluoro-15-crown-5-ether (PFCE), herein, we prepare PFCE nanodroplets with cisplatin prodrug (cisPt(iv)) conjugated phospholipids and other commercial lipids as the stabilizer to enable tumor targeted oxygen shuttling. The obtained PFCE@cisPt(iv)-Lip shows high physiological stability and efficient oxygen loading capacity. As vividly visualized under an in vivo photoacoustic imaging system, tumors on the mice with intravenous injection of such PFCE@cisPt(iv)-Lip show effective tumor oxygenation. Together with X-ray exposure, such PFCE@cisPt(iv)-Lip upon intravenous injection could induce severe DNA damage of cells, thereby remarkably suppressing the tumor growth and significantly prolonging their survival time without causing obvious toxic side effects. This work highlights PFCE@cisPt(iv)-Lip as an adjuvant nanomedicine for enhanced chemo-radiotherapy of tumors by attenuating hostile tumor hypoxia, indicating its promising potential for future clinical translation ascribed to its straightforward synthesis and notable tumor growth inhibition at a safe dose.

Stimuli-responsive nanocarriers for drug delivery, tumor imaging, therapy and theranostics

In recent years, much progress has been motivated in stimuli-responsive nanocarriers, which could response to the intrinsic physicochemical and pathological factors in diseased regions to increase the specificity of drug delivery. Currently, numerous nanocarriers have been engineered with physicochemical changes in responding to external stimuli, such as ultrasound, thermal, light and magnetic field, as well as internal stimuli, including pH, redox potential, hypoxia and enzyme, etc. Nanocarriers could respond to stimuli in tumor microenvironments or inside cancer cells for on-demanded drug delivery and accumulation, controlled drug release, activation of bioactive compounds, probes and targeting ligands, as well as size, charge and conformation conversion, etc., leading to sensing and signaling, overcoming multidrug resistance, accurate diagnosis and precision therapy. This review has summarized the general strategies of developing stimuli-responsive nanocarriers and recent advances, presented their applications in drug delivery, tumor imaging, therapy and theranostics, illustrated the progress of clinical translation and made prospects.

Synthetic immunity by remote control

Cell-based immunotherapies, such as T cells engineered with chimeric antigen receptors (CARs), have the potential to cure patients of disease otherwise refractory to conventional treatments. Early-on-treatment and long-term durability of patient responses depend critically on the ability to control the potency of adoptively transferred T cells, as overactivation can lead to complications like cytokine release syndrome, and immunosuppression can result in ineffective responses to therapy. Drugs or biologics (e.g., cytokines) that modulate immune activity are limited by mass transport barriers that reduce the local effective drug concentration, and lack site or target cell specificity that results in toxicity. Emerging technologies that enable site-targeted, remote control of key T cell functions - including proliferation, antigen-sensing, and target-cell killing - have the potential to increase treatment precision and safety profile. These technologies are broadly applicable to other immune cells to expand immune cell therapies across many cancers and diseases. In this review, we highlight the opportunities, challenges and the current state-of-the-art for remote control of synthetic immunity.

Herceptin-decorated paclitaxel-loaded poly(lactide-co-glycolide) nanobubbles: ultrasound-facilitated release and targeted accumulation in breast cancers

Ultrasound can promote the drug release from drug-loaded substances and alter the tumor local microenvironment to facilitate the transport of drug carriers into the tumor tissues. Based on the altered tumor microenvironment, nanobubbles (NBs) as drug carriers with surfaces functionalized with targeting ligands can reach the tumor sites, thereby increasing the efficacy of chemotherapy. Herein, paclitaxel (PTX)-loaded poly(lactide-co-glycolide) (PLGA) NBs are prepared as drug carriers with covalently conjugated herceptin (anti-HER2 monoclonal antibody) on the surface to guide the target. The effect of ultrasound on the drug release and targeting of the herceptin-conjugated drug-loaded nanobubbles (PTX-NBs-HER) on the cancerous cells is determined. The use of ultrasound significantly improves the cell targeting capability in vitro, and efficiency of enhanced permeability and retention in vivo. The combination of PTX-NBs-HER and ultrasound facilitates the release of PTX, as well as the uptake and cell apoptosis in vitro. The in vivo application of both PTX-NBs-HER and ultrasound enhances the PTX targeting and accumulation in breast cancers while reducing the transmission and distribution of PTX in healthy organs. The combination of ultrasound with PTX-NBs-HER as contrast agents and drug carriers affords an image-guided drug delivery system for the precise targeted therapy of tumors.

Gas-Mediated Cancer Bioimaging and Therapy

Gas-involving cancer theranostics have attracted considerable attention in recent years due to their high therapeutic efficacy and biosafety. We have reviewed the recent significant advances in the development of stimuli-responsive gas releasing molecules (GRMs) and gas nanogenerators for cancer bioimaging, targeted and controlled gas therapy, and gas-sensitized synergistic therapy. We have focused on gases with known anticancer effects, such as oxygen (O₂), carbon monoxide (CO), nitric oxide (NO), hydrogen sulfide (H₂S), hydrogen (H₂), sulfur dioxide (SO₂), carbon dioxide (CO₂), and heavy gases that act via the gas-generating process. The GRMs and gas nanogenerators for each gas have been described in terms of the stimulation method, followed by their applications in ultrasound and multimodal imaging, and finally their primary and synergistic actions with other cancer therapeutic modalities. The current challenges and future possibilities of gas therapy and imaging vis-à-vis clinical translation have also been discussed.

Bubble-Manipulated Local Drug Release from a Smart Thermosensitive Cerasome for Dual-Mode Imaging Guided Tumor Chemo-Photothermal Therapy

Thermosensitive liposomes have demonstrated great potential for tumor-specific chemotherapy. Near infrared (NIR) dyes loaded liposomes have also shown improved photothermal effect in cancer theranostics. However, the instability of liposomes often causes premature release of drugs or dyes, impeding their antitumor efficacy. Herein, we fabricated a highly stable thermo-responsive bubble-generating liposomal nanohybrid cerasome with a silicate framework, combined with a NIR dye to achieve NIR light stimulated, tumor-specific, chemo-photothermal synergistic therapy. Methods: In this system, NIR dye of 1,1'-Dioctadecyl-3,3,3',3'- Tetramethylindotricarbocyanine iodide (DiR) with long carbon chains was self-assembled with a cerasome-forming lipid (CFL) to encapsulate ammonium bicarbonate (ABC), which was further used for actively loading doxorubicin (DOX), affording a thermosensitive and photosensitive DOX-DiR@cerasome (ABC). Results: The resulting cerasome could disperse well in different media. Upon NIR light mediated thermal effect, ABC was decomposed to generate CO2 bubbles, resulting in a permeable channel in the cerasome bilayer that significantly enhanced DOX release. After intravenous injection into tumor-bearing mice, DOX-DiR@cerasome (ABC) could be efficiently accumulated at the tumor tissue, as monitored by DiR fluorescence, lasting for more than 5 days. NIR light irradiation was then performed at 36h to locally heat the tumors, resulting in immediate CO2 bubble generation, which could be clearly detected by ultrasound imaging, facilitating the monitoring process of controlled release of the drug. Significant antitumor efficacy could be obtained for the DOX-DiR@cerasome (ABC) + laser group, which was further confirmed by tumor tissue histological analysis.

Multifunctionalized Microscale Ultrasound Contrast Agents for Precise Theranostics of Malignant Tumors

In ultrasonography, ultrasound contrast agents (UCAs) that possess high acoustic impedance mismatch with the bulk medium are frequently employed to highlight the borders between tissues by enhanced ultrasound scattering in a clinic. Typically, the most common UCA, microbubble, is generally close in size to a red blood cell (<∼10 μm). These microscale UCAs cannot be directly entrapped into the target cells but generate several orders of magnitude stronger echo signals than the nanoscale ones. And their large containment and high ultrasound responsiveness also greatly facilitate to perform combined treatments, e.g., drug delivery and other imaging techniques. So multifunctionalized microscale UCAs appear on this scene and keep growing toward a promising direction for precise theranostics. In this review, we systematically summarize the new advances in the principles and preparations of multifunctionalized microscale UCAs and their medical applications for malignant tumors.

Photothermal-Enhanced Phase-Transition Nanodroplets for Ultrasound-Mediated Diagnosis and Gene Transfection

Gene therapy is one of the promising solutions in cancer therapeutics. Ultrasound-mediated gene delivery showed great potential as a noninvasive strategy for gene therapy. However, the efficiency of gene transfection and incorporation of multiple functions remain key challenges in the development of gene delivery systems. In this study, we developed perfluoropentane (PFP) and gold nanorods (AuNRs) loading nanodroplets for photothermal-enhanced ultrasound-mediated imaging and gene transfection. The nanodroplet theranostic system was formulated with fluorinated cationic poly(aspartamide) based polymer that encapsulated PFP, AuNRs, and plasmid DNA and was stabilized with a negatively charged poly(glutamic acid)-g-MeO-poly(ethylene glycol) (PGA-g-mPEG) coating. The nanodroplets presented good stability, biocompatibility, and DNA binding stability. Upon treatment with both near-infrared and ultrasound energy, the photothermal and ultrasound-responsive system exerted a synergistic effect, in which strong adsorption of light induced hyperthermia that promoted the phase transition of PFP and the following ultrasound irradiation, generating strong acoustic cavitation and sonoporation, thus leading to enhanced ultrasound contrast imaging and gene transfection efficiency both in vitro and in vivo.

GSH-sensitive Pt(IV) prodrug-loaded phase-transitional nanoparticles with a hybrid lipid-polymer shell for precise theranostics against ovarian cancer

Background: Platinum (II) (Pt(II))-based anticancer drugs dominate the chemotherapy field of ovarian cancer. However, the patient's quality of life has severely limited owing to dose-limiting toxicities and the advanced disease at the time of diagnosis. Multifunctional tumor-targeted nanosized ultrasound contrast agents (glutathione (GSH)-sensitive platinum (IV) (Pt(IV)) prodrug-loaded phase-transitional nanoparticles, Pt(IV) NP-cRGD) were developed for precise theranostics against ovarian cancer.

Methods: Pt(IV) NP-cRGD were composed of a perfluorohexane (PFH) liquid core, a hybrid lipid-polymer shell with PLGA_12k-PEG_2k and DSPE-PEG_1k-Pt(IV), and an active targeting ligand, the cRGD peptide (PLGA: poly(lactic-co-glycolic acid), PEG: polyethylene glycol, DSPE: 1,2-distearoyl-sn-glycero-3-phosphoethanolamine, cRGD: cyclic Arg-Gly-Asp). Pt(IV), a popular alternative to Pt(II), was covalently attached to DSPE-PEG_1k to form the prodrug, which fine-tuned lipophilicity and improved cellular uptake. The potential of Pt(IV) NP-cRGD as contrast agents for ultrasound (US) imaging was assessed in vitro and in vivo. Moreover, studies on the antitumor efficiency and antitumor mechanism of Pt(IV) NP-cRGD assisted by US were carried out.

Results: Pt(IV) NP-cRGD exhibited strong echogenic signals and excellent echo persistence under an US field. In addition, the GSH-sensitive and US-triggered drug delivery system maximized the therapeutic effect while reducing the toxicity of chemotherapy. The mechanistic studies confirmed that Pt(IV) NP-cRGD with US consumed GSH and enhanced reactive oxy gen species (ROS) levels, which further causes mitochondria-mediated apoptosis.

Conclusion: A multifunctional nanoplatform based on phase-transitional Pt(IV) NP-cRGD with US exhibited excellent echogenic signals, brilliant therapeutic efficacy and limited side effect, suggesting precise theranostics against ovarian cancer.